


The Cake's Crumb

by Krexxal



Series: Cake's Crumb Universe [1]
Category: Phineas and Ferb
Genre: F/M
Language: English
Status: Completed
Published: 2020-09-15
Updated: 2020-09-30
Packaged: 2021-03-08 04:08:30
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 8
Words: 14,030
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26639335
Author URL: https://archiveofourown.org/users/Krexxal/pseuds/Krexxal
Summary: Phineas got to read Isabella's letter when the Un-Retrograde Inator hit Ferb instead. However, he was not prepared for what would result both mentally and literally. Meanwhile, Dr. Heinz Doofenshmirtz has enacted a plan that even he didn't plan for thouroughly, and now he has to deal with the aftermath of his own actions.
Relationships: Phineas Flynn/Isabella Garcia-Shapiro
Series: Cake's Crumb Universe [1]
Series URL: https://archiveofourown.org/series/2039146
Comments: 9
Kudos: 28





	1. The Truth

**Summary for the Chapter:**

> A letter Isabella wrote for Phineas enters his hands, with revelations within. Meanwhile, Dr. Heinz Doofenshmirtz prepares for his next scheme.

"Come back here! Now I've got-"

Within a large, purple room, a teal-furred platypus with a fedora was fighting a large robot resembling a human in a suit.

Clinging to the bottom of a large, spherical machine, he pulled a lever as it rotated, whacking the robot as he was interrupted mid-sentence.

"...rhythm?"

The platypus then dashed off as the machine fired off a large green beam. Wiping sweat off of his brow, Perry sighed in relief. Today's Doofenshmirtz scheme was just as ridiculous as ever. Who would want to make something move backwards? What practical use would that have?

* * *

Out of all possible words Isabella Garcia-Shapiro could use to describe her day, "stressed" was the best one.

She had just trailed a letter she had regretted sending all over Danville, alongside her troop of Fireside Girls, as it made its way towards its intended destination: the Flynn-Fletcher household, home of one Phineas Flynn. For years, Isabella had admired the redheaded kid, to the point where she became infatuated with him. She had tried countless times to drop hints to him, to offer him subtle cues, to asking to spend time alone with him, but Phineas was...dense. Oblivious. Blind. The list went on. After a visit to her Nana today, Isabella had been motivated to send Phineas a letter explaining her true feelings, but soon regretted it as it made its way to his house.

Right into his hands.

Phineas eyed the letter alongside his green-haired brother Ferb.

"Oh, look! It's from you Isabella!"

_Well Isabella, here it is. He's finally going to know how you feel. There's no turning back now. At least you told the truth and you spoke from your heart. I can accept this._

Phineas carefully opened the envelope, before unfolding the letter. As he did so, Isabella still clung to her heart. What would he think of it? Would he reject her on the spot? Would he rip it up and laugh at her? Would he simply not understand what she's trying to convey?

"Dear Phineas...aw, and there's a little heart."

Suddenly, at that moment, a green beam of energy flew across the street, seemingly towards Phineas. Ferb eyed his brother before pushing him to the ground and taking the hit.

"Ferb, what are you-"

Immediately, Ferb was acting...strange. He walked backwards as he tore apart the takeout artwork he and Phineas had worked on all day. Phineas couldn't help but put the letter aside as he, Isabella, and the nearby Fireside Girls observed Ferb's impressive handiwork, following him to the backyard as they did so. Just as Ferb had finished disassembling it, Candace, the Flynn-Fletchers' older sister, walked out to the backyard with their mother Linda in tow.

"Awww! Of course."

Candace groaned to herself slightly. Another day, another failed bust.

"There was like a whole bunch of stuff the boys were clearing out!"

"Speaking of 'stuff', what's up with your room?"

Candace looked towards her mother with an expression of disappointment.

"Yep. I'm on it."

As Candace walked into the house, Linda followed, likely to make sure she followed through with cleaning her room while the rest of the kids conversed among each other.

"Ferb, why did you do that?"

"I...don't know."

As Ferb responded, everyone looked to Phineas, who was still holding Isabella's letter.

"I'm sorry, but I was so distracted by...whatever it is that just happened that I lost focus. Isabella, is it ok if I read this letter later tonight?"

"Sure Phineas!"

Isabella sighed internally to herself. She had been glad to have the opportunity to see Phineas's personal reaction initially, but now she would have to wait. Such was the life of the romantic.

"In that case, let's head back to the lodge girls. We've got patch planning to do."

"Aye aye chief!"

As Isabella and her friends left, she couldn't help but look back wearily to Phineas. Sighing to herself, she exited the backyard.

Tomorrow had the potential to either be the best day of her life, or the worst day of her life.

* * *

Within Doofenshmirtz Evil Incorporated, Dr. Heinz Doofenshmirtz was busy recovering from his climactic battle with Perry the Platypus, especially since he was covered in soot from his own coin-operated self destruct button. His loss of the Un-Retrograde Inator was a big one, and he had just hoped it didn't hit anything useful.

"Sir, are you alright?"

"Oh shut up Norm. You're the last one who should be talking here."

As Heinz got up, he gave Norm a steely glare. While he was one of his more successful creations, Norm was also an idiot. Part of him wondered if it was because of his own incompetence.

"Sorry sir."

Heinz walked through his wrecked laboratory as he got to his desk and opened up his laptop. It was a common habit of his to prepare for the next day's scheme almost immediately after Perry the Platypus had stopped his last one.

"Let's see...let's see...what kind of inator should I do for tomorrow..."

"How about an inator that lets you impersonate someone? I know you've been having trouble with pizza deliv-"

"Can it Norm! That's a stupid idea!"

* * *

"And then Ferb was suddenly zapped by a laser and began dismantling what we made for the day!"

At the dinner table, Phineas was busy recounting the day's events with the family. While his parents, Lawrence and Linda, presumed he just had an active imagination, everything he had described was real and happened.

"Oh, you kids have such an active imagination. Candace, I remember when you were this imaginative."

On the other side of the table, Candace had her head on her fist as her elbow rested on the table, making a pouty face of sorts as her father spoke to her. Busting her brothers had almost never yielded results. The closest she had even gotten to it was in a dream for crying out loud!

"Yeah, yeah."

As Candace pouted, Phineas and Ferb put their empty plates up by the sink, eyeing their pet platypus Perry on the ground, before yawning.

"I think we'll retire for the night. It's been a long day."

"Night boys!"

As their mom wished them good night, Phineas and Ferb went upstairs and got ready for bed. Before Phineas could get into bed however, he eyed a pink piece of paper on his nightstand.

"Right, Isabella's letter! I should give it a read."

Phineas sat in bed as he grabbed Isabella's letter, before thinking to himself. What would warrant her writing a letter just for him? He unfolded the letter oncemore before giving it a read at last.

_Dear Phineas ,_

_After years of contemplating, thinking, and nearly acting on instinct, I've decided to finally express something I've been meaning to tell you for a while. Something I cannot hold any longer. Phineas Flynn, I like you. And not just the friend kind of liking. I like you like you._

_When my family first moved to Danville across the street, it was you who guided me around. You who introduced me to all of these wonderful people. It was your energy for life and desire to make people happy that made me fall for you. I...I love you my little crumb cake. More than you know. I just hope you feel something out of reading this letter, even if it isn't what I'm feeling._

_-Isabella Garcia-Shapiro_

* * *

"Inator ideas, come to papa! Come to...oh, that's right."

Doofenshmirtz sat at his desk in front of his computer with an empty desktop. He was having evil scientist's block. Why was it that he couldn't think of any good inator ideas? Was it the naming convention? His philosophy? His inclusion of self-destruct buttons?

"Sir, why don't you rip off someone else's blueprints from the Inter-"

"I know! I'll steal someone else's blueprints off the internet and repurpose them as my own! Now THAT'S evil!"

Norm simply frowned as Doofenshmirtz opened up Google Chrome and began searching for blueprints. The top result was a website called " ", which he immediately clicked on.

"I remember getting some sort of gravity inator from here, and it worked well! Maybe I can steal some others too."

After several hours of searching, getting coffee, and working without sleep, Heinz finally had a breakthrough and downloaded two blueprints. The first was for a supercomputer of sorts that could answer any question, while also being a powerful enough computer to assist Heinz in his own evil endeavours. The second wasn't as major as the supercomputer, but still had its uses: it was a blueprint for an exoskeleton suit of sorts that had a beaked helmet.

"Norm, I know what we're going to do tonight."

* * *

As he put down the letter, Phineas immediately laid down on his bed. His mind was racing, his heart was beating, and his emotions were sparring with one-another. Isabella liked, no, LOVED him. Phineas was no stranger to helping others with romantic pursuits, but knowing that someone else had a thing for him was a different feeling entirely. Immediately, Phineas couldn't help but think back to many of the experiences the two of them had together over the course of the summer.

_That helmet looks so manly._

_You had me at OUR grandchildren._

_You want me to go on a romantic cruise with YOU?_

_That's too bad. I thought the two of you, you know, a boy, a girl, alone in the City of Love. I thought romance was a forgone conclusion._

_Well that's not the Phineas Flynn I fell in...to this situation with._

_So, uh, Phineas, I was wondering if maybe after this, you'd like to go to the premiere of the new Stumbleberry Finkbat movie._

Phineas lay on his bed, staring at his ceiling as he pondered what just happened. He couldn't deny that Isabella was cute, but at the same time...he felt disappointed in himself. He felt angry at himself for ignoring her for almost the entire summer. For being this dense. A single tear fell down his chin as he tried to sleep, but to no avail.

* * *

And across the street, someone else struggled to sleep too. Isabella had endured one of, if not the most stressful days of her life, and was struggling to sleep. How would tomorrow unfold? Would it be good? Would it be bad?

Neither of them knew yet.


	2. Every Day's A Brand New Day

**Summary for the Chapter:**

> Phineas talks to Candace and goes for a walk to clear his head. Meanwhile, Heinz finalizes his plan.

The time was six-thirty in the morning, and Phineas Flynn was having a rude awakening. All night he had been tossing and turning, unable to sleep due to the revelations contained within Isabella's letter for him. How could he have mistreated her so poorly? How could he have not picked up her advances? Phineas hated to admit it, but he felt...sad. The last time he was this emotionally upset was when he was stranded on the island after the Sun Beater 3000 crashed.

A situation which Isabella had brought him out of.

Just as Phineas was about to continue moping in his head, he heard the sound of a door opening. Getting up, he noticed Candace was walking to the bathroom. This was nothing unusual for him: Candace often woke up early to get a head start on busting her brothers, something which Phineas still didn't understand to this day. As Phineas got back into bed, he looked towards Ferb's bed, sighing to himself. Maybe he did need to talk to someone about the letter. However, Phineas was unsure if Ferb would be the right person to bring it up to. Ferb was moreso a man of action, not so much words. Deep down, Phineas knew he had to talk to someone who was in a relationship currently.

And that someone was walking back into their bedroom from the bathroom.

* * *

After nearly eleven hours of nonstop planning, building, and the occasional mistake, Heinz Doofenshmirtz was almost finished the supercomputer. As he revised the blueprints, one thing came to mind.

"Crap, I need a...a restraining bolt. Norm, can I borrow your restraining bolt?"

"You said you were too cheap to buy me one!"

Heinz planted the palm of his hand right onto his face.

_Right, that was the week where Charlene's alimony cheque came in late. I'd need to buy one when the store opens in-wait a minute. I can just use Norm as the core of the computer and add to his processing power! It's not like he'll turn on me any time soon. Heinz, you're a genius!_

Heinz quickly made a few modifications to the computer's core, before finishing his work and beckoning Norm over. Before him stood a large, Norm-shaped hole in the core.

"Norm, head on in here. Do Heinz a favor old buddy."

"Yes sir!"

Norm immediately walked into the computer, before having the wires and cables immediately connect to his body. As the computer turned on, Heinz grinned before hearing a familiar voice.

"I feel so much smarter sir!"

"Good Norm, good. Do a scan of the Tri-State Area."

Norm began emitting red beams across the sky as they spun around the Tri-State Area, analyzing it and collecting data. Norm's face seemed to be in a trance as it did so.

"Gathering data from all objects and habitants. Computing all logical outcome of all events."

* * *

Candace sat on her bed, scrolling through social media on her phone, something she usually did if Phineas and Ferb hadn't woken up yet. Then, she heard a knock as her door slowly opened.

"Hey Candace, you got a minute?"

Candace looked to her door to see Phineas standing by in his pyjamas, sighing to herself. Was he working on his next bustable project already? However, before she could ask him what he was doing, Candace noticed that something seemed...off about Phineas. He lacked his usual happy expression, which was replaced with a more somber one.

"Yeah, sure."

Phineas opened the door before closing it and sitting on Candace's bed next to her.

"So this is going to sound weird but...how long were you crushing on Jeremy for before the two of you got together?"

Candace smiled slightly as Phineas mentioned that, not even questioning the fact that it was coming from his mouth.

"Since the second grade. He was so cute then! I just remember when he was in the school play and played the role of-"

"I see. Now, suppose Jeremy hadn't noticed your...advances this summer. How would you have reacted?"

_There it is. There's one of the deep questions Phineas is known for asking._

"Well, I suppose I would've kept going. You know me, I'm not one to give up. Wh...why are you asking me this?"

Upon hearing those words, Phineas sighed to himself. Did he tell her? Or would he go another route?

"Let's just say I'm the Jeremy to someone's...someone's Candace, and I'm not sure how to react."

Phineas hugged Candace before walking out of the room, looking back at her.

"Sorry to have bothered you."

As Phineas left, Candace blinked to herself a few times, struggling to process what just happened. Eventually, it dawned on her as she lay down on the bed and simply smirked to herself.

* * *

Eventually, after about ten minutes of Norm scanning the Tri-State Area, Heinz heard a ding.

"Done."

"I suppose it's time to put you to work then. What can you do?"

"I can answer any question you'd like, no matter how big or how small. My vast intellect is ready to be tested."

Heinz shuffled back and forth briefly as he brainstormed. What could he ask Norm the answers to? Eventually, the obvious dawned on him.

"Norm, I have a question...and an assignment for you."

"Let's hear it!"

"Can you put that exoskeleton blueprint to use in some sort of project? I could never figure out how exactly to use it. Do I wear it? Do I hire someone to wear it? Do I use it to build something? I have no idea."

"Sure thing!"

Heinz grinned to himself. He was ready for the big hitter.

"And now for my question. How may one conquer the Tri-State Area?"

* * *

Ferb had a bit of a rude awakening, especially with Perry deciding to lay on his side where Ferb would normally get out of bed. As he woke up, he noticed that Phineas's bed was empty. Ferb simply shrugged, knowing that his brother was likely preparing for today's big project early. He made his way downstairs, seeing that his parents were already awake. His mother looked at him a bit worriedly.

"Morning Ferb, have you seen Phineas?"

Ferb shook his head in response, but was a bit worried. If mom and dad hadn't seen him, where was he?

"It's not like him to miss breakfast."

Ferb decided to check back upstairs for Phineas oncemore, gaining a look from a worried Perry as he walked up the stairs. Maybe he just couldn't see him in bedfrom the angle he was looking at. Walking into the room, he saw nothing, save for one small detail on the nightstand: a pink letter.

Isabella's letter.

Ferb knew better than to read it. This was private after all! However, he could suspect what it was about judging by what Milly had told him the other day, more specifically the fact that Isabella referred to Phineas as her "little crumb cake". Whatever the case, this letter had created some sort of emotional reaction for Phineas.

* * *

Isabella groggily got out of bed, wiping her eyes before walking over to her bedroom window. From here, she had a great view of the Flynn-Fletcher household. Leaning on the counter, she sighed to herself as she thought about the night before. Phineas had likely read her letter, and she knew that by visiting him that day, she would finally hear what he had to say about her.

_Isabella, you need to get over there pronto. You can't just hide from him and expect him to come to you._

Isabella breathed in as she quickly showered and got some clothes on, before rushing over to the Flynn-Fletcher backyard. As she walked over, she began to think to herself.

_It's now or never Isabella. You need to find out what he thinks._

Isabella breathed in upon nearing the house, looking at it and continuing to think. Phineas...meant so much to her. She wanted nothing more than to spend some time with him alone, to show him how much she cared. And if she kept shoving it inside, it'd make her sick. Isabella knew she had to make her stand. Throwing open the backyard gate, she was ready for what was to come.

"Hey Phineas, whatcha-"

Isabella quickly stopped as she noticed that Phineas wasn't present in the backyard: just Ferb. Looking around, she sat down next to him.

"Ferb, do you know where Phineas is? I need to talk to him."

"I'm...not sure. I was actually hoping you might be able to help me figure that out."

* * *

Phineas walked through downtown Danville, hands in his pockets. He felt bad for leaving the house so quickly, but knew he needed some time to himself. Time to figure out his exact thoughts.

At this point, Phineas couldn't deny that he had some sort of feelings for Isabella. After all, he wouldn't have built an entire haunted house to cure the hiccups of everybody he knew. No, there was a connection. Phineas felt it, but wondered if he had squandered it. She was a good friend, no, a great friend. Someone he could rely on. Someone he trusted.

Someone he loved.

Hearing those words in his mind made Phineas shake a bit. Love was something that was...complicated to him. While he was more than happy to help his friends with their love lives, he hadn't given much thought to his own. He had been so busy with his projects all summer that it had completely slipped his mind. Taking a seat on a bench, Phineas put his head inside his hands before crying to himself.

* * *

Far above the Danville skyline, Perry was flying through on his hover car. Looking down at the ground, he noticed a red-haired boy crying on a bench, but was quickly interrupted by his car's computer screen, where his superior, Major Monogram, appeared.

"Morning Agent P. We noticed a major surge of electricity coming from Doofenshmirtz's building early this morning. Investigate at once."

Perry saluted the screen as it turned off, before landing his car on a building just across from Doofenshmirtz Evil Incorporated. Grabbing a grappling hook, he shot it at Doofenshmirtz's building before pulling himself up to it. Upon arriving at the ever-familiar ledge in the middle of the building, Perry noticed that the interior was dark. Empty. Devoid of light. Carefully sneaking through, he suddenly heard the sound of clanking metal. Perry proceeded to hide behind a crate, failing to notice that he had hit a button on the back of the crate. Immediately, a warning siren began to ring throughout the building as two large, imposing robots cornered him. Their heads resembled that of a bird, with a beaked flap at the front. The two robots lifted up Perry as more lights revealed themselves.

"Welcome to my funhouse Perry the Platypus!"

Perry growled slightly. That wasn't Heinz's voice, something that became apparent when a large, imposing computer screen turned on within the building. A familiar face showed itself on it.

"It's me, your old pal Norm!"

"And Heinz Doofensh-"

Immediately, Heinz had rushed down the stairs before tripping and falling over countless times, right into a bookshelf. Getting up and dusting himself off, he walked over to his nemesis with a grin on his face.

Today was his day of reckoning.


	3. Pondering

**Summary for the Chapter:**

> Isabella, Ferb, Buford, and Baljeet begin a search for Phineas. Meanwhile, Heinz is in for a shocker when his plan goes off the rails, and Phineas gets some more advice.

The sun beat down on the Flynn-Fletcher backyard early in the morning. Isabella, Ferb, Buford, and Baljeet were sitting around the usual tree, protected from the sun by the leaves above. The atmosphere seemed somber. Buford was scratching the grass. Baljeet was twiddling his fingers. Ferb was flipping through a notepad. As for Isabella, she was simply looking down at the ground with a sullen expression. For her, this was quite a situation. Why would Phineas just go missing? Was it because of something she had said in her letter? Was it how she delivered it, was it her stress over the whole "crumb cake" nickname? Whatever it was, it gave her an expression of discontent on her face.

"Maybe we can get Dinnerbell back by singing a song on a roof like we did for Perry."

"Buford, that's ridiculous and sounds cliche. How does music assist us with finding someone missing? I suggest applying some sense of logic here."

"What? Emotionally-driven musical talent works every time for us, Baljeet!"

During Buford and Baljeet's argument over the power of searching for people via singing, Isabella leaned along the bumpy, mossy tree trunk, deep in thought. Somehow, she felt guilty for all of this. If she hadn't sent Phineas the letter, he likely wouldn't have vanished. She had written it without taking into consideration how HE would feel.

"I'm just saying, music makes people happy!"

"But it's completely ridiculous and-"

"WOULD YOU TWO SHUT IT FOR ONE SECOND!"

Almost immediately, everyone turned their gazes towards Isabella. She glanced back at herself and sighed after her… outburst.

"It's...it's my fault. I shouldn't have sent him that letter. And to think that I told him everything in it..."

The other kids looked at each other for a few seconds as Isabella shed a tear. Buford was the first to break the silence, smirking at Baljeet.

"I guess someone owes me money."

Baljeet grumbled, fishing a $20 bill out of his pocket and handing it to Buford before looking back towards Isabella.

"At first I was worried about Phineas flat out rejecting me on the spot. Now though… I'm worried about him, I… I..."

Isabella burst into tears as Ferb patted her on the back and both Buford and Baljeet looked on in sympathy.

Then, Buford stood up triumphantly, coughing into his hand before putting his fists on his shoulders.

"Well, we'd best find him then! It's what Dinnerbell would want us to do!"

Baljeet, Isabella, and Ferb looked to Buford with smiles on their faces, with Isabella feeling her tears drying up.

"For Phineas."

Baljeet joined Ferb right after, throwing his fist into the air in victory.

"For Phineas!"

After a moment's hesitation, Isabella got up off her feet, cheering alongside the others.

"For Phineas!"

* * *

"So, Perry the Platypus, I see you've met the new Norm."

Heinz Doofenshmirtz stood before Perry within his laboratory, where large numbers of computer consoles, spare blueprints, and prototypes dotted the floor. Many of them were broken, some had scorch marks, and as a whole they looked quite incomplete. Of particular note to Perry was the lack of an Inator in the lab, something which he normally expected from Doofenshmirtz. He struggled to break free, but the two robots keeping him restrained had grips of iron, twisting his muscles and keeping him immobilized. Towering above them was a large monitor bearing Norm's face, illuminating the room.

"You're probably wondering what inator I have planned for today, Perry the Platypus. What emotionally scarring backstory I have to tell you. What genius plan I have in my pocket in my latest attempt to conquer the Tri-State Area."

Doofenshmirtz paced back and forth, before flashing Perry a wicked grin.

"The thing is, this plan doesn't have any of this! I souped up Norm with this supercomputer blueprint I downloaded, and he was the one who devised the rest of the plan for me!"

"And now, it's time for the next step!"

A red light flashed on Norm's computer monitor as an electric current raced through Perry's body. He felt the pain of many, many volts of electricity within him, his fur spiking. As Perry was panting in exhaustion, Heinz looked on with a face of discontent. He didn't want Perry to be this injured from their scuffles.

"Wait wait wait! You can't torture Perry the Platypus! He's supposed to break free and then thwart our plan! That's the whole system we have going here!"

Norm's eyes turned towards Heinz with a steely glare.

"But Dr. D, you asked me how one can conquer the Tri-State Area. You never specified that you wanted to keep Perry alive."

Heinz smacked his face with the palm of his hand as he looked up at Norm.

"Well it's my plan and I'm changing it!"

"Correction: it's my plan, Heinz. You told me to enact the plan, but didn't specify that it was in your name."

Cold, hard reality was starting to set in for Heinz. Norm was going to take this plan too far, and not even to his creator's benefit! If Norm conquered the Tri-State Area, Heinz would never be able to take it over for himself.

"In that case, you've forced my hand, Norm!"

Heinz fished a remote out of his pocket with a self-destruct button on it, slamming his fist onto it. The two robots holding Perry spontaneously combusted, freeing the platypus from Norm's clutches as his eyes gazed at the duo.

"Activating Omega-class defense systems."

As Heinz grabbed Perry and bailed for the balcony, lasers and traps emerged within the laboratory beneath Norm's shadow. Fortunately, Perry was nimble enough to get himself and Heinz through them before grabbing his grappling hook and firing it at the building where his hovercar was parked.

"Are you sure this thing can-YAAH!"

Doofenshmirtz's plea was interrupted by Perry swinging off the balcony, Heinz in tow. Miraculously, the grappling hook was able to hold up the two of them, albeit with a strained string, as they swung onto the nearby building and got into Perry's hovercar. As they flew off, Perry sighed to himself. Once again, Doofenshmirtz had screwed up and needed to work with him to fix his problem.

And back at Doofenshmirtz Evil Incorporated, Norm was furious. The loss of Perry and Heinz meant that he needed to adjust his plan for conquest accordingly.

No compromises would be made.

* * *

Ferb and Isabella were walking down the streets of Danville, keeping an eye out for Phineas. Buford and Baljeet had peeled away from the group earlier to cover more ground, though Buford had also mentioned wanting to grab a bite to eat and needing to 'keep his nerd with him'. As they passed the Googolplex Mall, Isabella continued to think to herself.

"I don't get it, Ferb. This is completely unlike him."

Ferb glanced back at Isabella.

"The last time I saw Phineas this distraught was when we were on the island and he dug up that sponge and starfish. And the one time I decide to tell him how I really feel, he goes missing! I know he's been dense this summer, but I didn't think he'd be hiding from me like this."

Isabella shed a tear as she looked around the city. Danville was always busy with the blaring of horns and the sound of pedestrians walking. There was no sign of Phineas, but she knew better than to give up hope. That was something he never did, even in their darkest hours.

"But you know what? We'll find Phineas. We'll bring him home, and I'll be able to tell him in person how much he means to me. Ferb… thanks for listening."

Ferb nodded as Isabella smiled to herself. She knew it was up to her to bring Phineas back, for all of their sakes.

* * *

Phineas stumbled into a Mr. Slushy Burger in downtown Danville, heading towards the front desk. His body ached, his muscles felt tense, and his mind was still racing. His stomach was growling, and Phineas knew this needed to be alleviated. He got in line as the customer in front of him picked up his order. Once the customer in front was gone, Phineas approached the counter to see that Jeremy was working today.

"Welcome to Slushy Burger, can I take your-"

Jeremy was interrupted by his own bewilderment upon seeing Phineas, or more specifically, the state he was in. This was completely unlike him. The happy go-lucky inventor was… a wreck.

"...Phineas? Are you okay?"

"N-not really. I'll just take a large hot dog and a cola."

"Gotcha buddy. And hey, if you don't mind, I'm more than happy to help you out. I'm about to take my break anyways."

Phineas smiled slightly as he slid the payment for his food over the counter, got his order, and sat down. A few minutes later, Jeremy sat down next to him with a drink in hand.

"So what's bothering you?"

"I was sent a letter by Isabella and as it turns out she lik-no, loves me. I don't know what to do."

Jeremy smirked in response as he sipped his drink.

"Well, do you like her back?"

"I do, but something feels wrong. I've never been smart with this stuff and I feel like I've made Isabella upset. Would she forgive me for how I've treated her?"

"You remind me of what I was like with Candace."

Phineas looked towards Jeremy with an expression of surprise, but also curiosity.

"Candace had been crushing on me for years. And somehow, I didn't notice. It wasn't until this summer that my eyes were opened and I realized I liked her back. If I'm being honest, I kind of have you guys to credit for that."

Phineas stared blankly as his mind raced. It was true: the summer had created memories that Jeremy and Candace cherished and that brought them together. This time, it was a matter of doing that for himself and Isabella.

"Phineas? Phineas?"

Phineas jolted to attention as he noticed Jeremy again. Sighing to himself, he looked back towards the blond-haired boy.

"I'm alright."

"Good, buddy. Just go talk to her, man! Tell her how you feel! If she really does love you as much as she says, she'll forgive you for what happened this summer."

Upon hearing those words, Phineas's mind got to work and began thinking about the possibilities. If Isabella loved him that much, she'd accept him for who he is even after what's happened. After all, the summer belonged to him. Not doing anything would be the worst option.

"You know what? You're right!"

Phineas made his way to the door in a hurry. Jeremy followed not far behind.

"Phineas, what are you doing?"

"I'm going to go tell Isabella how I feel! Thank you, Jeremy!"

Phineas bolted out the restaurant, determined to accomplish his goal. Jeremy stood idle for a few seconds before grinning.

"Good for him."


	4. Gathering Storm

**Summary for the Chapter:**

> A broadcast is sent by Norm all over the Tri-State Area as our heroes react to it and prepare for the inevitable.

Across Danville, right as the clocks struck one, electronic devices, televisions, cellphones, and computers all began to show static, creating mass confusion and hysteria. People were screaming that it was the end of the world, while others thought it was just a signal issue.

That is, until the screens changed, and the visage of a robot emerged on every single device in the Tri-State Area.

"Attention citizens of the Tri-State Area. My name is Norm, and I will soon rise to power over this city. As I speak, my robot armies are growing and preparing to conquer all that stand in my way. This message serves as an ultimatum to those who are watching."

"Surrender, or be destroyed."

* * *

After seeing Norm's broadcast, Perry hurriedly landed the hovercar on the rooftop of a diner in downtown Danville, Doofenshmirtz in tow. Heinz was in a state of panic, pacing along the rooftop and muttering to himself.

"It's like you always tell yourself Heinz, your inators work, but you just don't use them properly. And this time, you DEFINITELY did not use it properly! Now you've got Norm about to conquer the Tri-State Area and-"

_THWAP!_

Perry slapped Heinz across the face with the back of his hand. He fell towards the side of the hovercar, placing his hand over the now-dark pink bruise. It hurt like hell.

"You know, it's rude to slap your friends, Perry the Platypus. But you're right, I screwed up. Again."

Heinz slouched on the side of the roof, his legs dangling over the street below. He sighed to himself. This was his worst plan yet. As he stared into the distance, Perry put a hand on his shoulder, smiling. He knew that him and Heinz had an odd relationship of sorts compared to most enemies: they were moreso frenemies, both fighting each other and occasionally aiding each other like with their trip to Feebla-Oot and their trek through the desert.

"Thanks, but I don't know what we can do. OWCA likely wouldn't accept my aid and-"

Perry chittered as he pointed out towards the streets of Danville, at what appeared to be warehouses. Heinz immediately leapt to his feet.

"You're right, Perry! We can use my old Inators! That'll show Norm."

Perry smiled as he jumped into his hovercar. They soared off the rooftop towards the warehouse district.

* * *

Phineas was dashing like a madman through the busy streets of Danville. The broadcast had forced him to take a shorter route home which he wasn't used to, his mind racing. He wanted to make sure Ferb was okay. That Candace was okay.

That Isabella was okay.

As Phineas ran through an already-panicked city, he was nearly hit by a car twice, something which he was normally more aware of. His parents were out of town for the day to attend an antique convention in Seattle. That left Phineas with only two family members in the city to locate. As he arrived on his street, Phineas noticed that his backyard was devoid of any sort of massive project, making him wonder if his absence had affected Ferb to a large degree. Phineas opened the door as he looked around the house.

"Candace? Ferb? You guys home?"

Nobody responded. That is, until Phineas heard something. It sounded like crying to him, and was coming from the basement. Carefully stepping down the stairs, Phineas heard the tears getting louder and louder, before finding the source: the Flynn-Fletcher panic room. Upon opening up the crate that concealed it, Phineas heard a familiar ear-piercing shriek.

"Candace?"

"Phineas?"

Phineas stepped down the ladder to find Candace shaking in the corner of the panic room with her teddy bear, Mr. Miggins, in hand. She looked absolutely terrified.

"Candace, are you okay?"

"No, I'm NOT OKAY! WE'RE GON-GONNA BE SLAVES TO THE ROBOTS AND I'M NOT READY FOR THAT! AAAAAAAH!"

Candace burst into tears as Phineas looked at her with a frown on his face. This wasn't like Candace at all. It was up to him to help her.

"It'll be alright. We've been through worse after all! Remember the time when you were abducted by aliens and we saved the planet?"

Candace formed a small smile as she looked to Phineas uneasily.

"R-right. But this is different. You sure we can do this?"

Phineas gave Candace a smile back as he stood up.

"Absolutely. We'll save Danville. We'll save our friends. We'll save the ones we love!"

"Y-yeah. I've got Jeremy, and you h-have Isabella."

Phineas smiled slightly upon hearing those words as the two of them exited the panic room, with Phineas heading upstairs to his room. Before he had left the house earlier that morning, he had left his phone behind to make sure he was free of distractions. Pulling it up, he found numerous missed calls, texts, and voicemails from his friends, most of them coming from Isabella understandably. One particular text caught his eye.

_I hope you're okay my little crumb cake. Call me as soon as you can._

Phineas blushed a bit as he read the text. Isabella had picked a cute nickname for him. Maybe he needed to think of a nickname for her.

* * *

After seeing the broadcast, Isabella and Ferb made a mad dash through the city. Panic and fear gripped the two kids as they made their way to the park, where they agreed to meet up. After all, they'd been through similar situations before. They eventually arrived to find Buford and Baljeet sitting by the fountain in the park with regretful looks on their faces.

"Buford and I could not find Phineas. And to think that he's out there in the middle of this...situation."

Isabella shed a tear as she sat down, with Ferb following suit. The grass tickled her legs slightly, but that wouldn't do much to cheer her up.

"I hope he's okay. I really do. I..."

Isabella felt her cheeks getting hotter and her eyes about to let loose a waterfall of tears. That is, until everyone felt a vibration in their pockets. They had all received texts.

From Phineas.

_Hey guys, meet me at the house as soon as you can. I've figured out a plan to stop the invasion._

Everyone looked at each other as they sighed in relief. Their search was over.

"If there's one guy who's always getting to work, it's Phineas."

"You said it, Buford!"

Everyone got up, Isabella smiling to herself through the tears. Phineas was okay. Even better, he was still himself! This was why she fell in love with him in the first place.

* * *

In the backyard, Phineas and Candace were hard at work on contraptions to halt the impending invasion. Some were based on old projects. Others were new designs. Phineas had built another baseball launcher akin to the one he had used in his battle alongside Meap earlier in the summer, as well as various other pieces of equipment. While Candace was no Ferb in regards to mechanical knowledge, she still played her part nonetheless, handing Phineas spare tools and making minor adjustments. While the urge to bust was strong for her, she knew that there was a more pressing issue at hand.

"The rest of the gang should be here soon, Candace."

"You're not worried about seeing Isabella again?"

Phineas briefly halted adjusting a screw on his baseball launcher as he looked to Candace, sighing.

"I want to tell her how I feel, but now's not the time. We have a bigger problem."

"I see."

Phineas and Candace returned to their work, up until they heard the sound of footsteps. Turning their gazes towards the gate, they saw Isabella, Ferb, Buford, and Baljeet standing before them. While Candace gave them all a wave, Phineas couldn't help but stare at Isabella for a few seconds before shaking his head. This had been the first time he'd seen her since the letter was mailed, and he felt some sort of feeling in his stomach. Isabella too was also in a small trance as she looked at Phineas, her heart beating faster and faster. Was he okay? Did he have things to tell her? Isabella was eager to find out as she attempted to speak.

"Hey."

"Hi."


	5. Together

**Summary for the Chapter:**

> Phineas and Isabella have a chat about the letter. Meanwhile, Ferb and Gretchen get closer, and several old inators of Heinz's are tested with disastrous results.

**Notes for the Chapter:**

> A new chapter has arrived! This one took quite a bit of time to iron out, but I hope you enjoy!

About five minutes had passed since the arrival of the gang to the Flynn-Fletcher household. Now, everyone was gathered before Phineas and ready to hear him speak. Behind Phineas were several large objects covered in tarp, alongside a sealed crate. The gang, save for Candace, knew nothing about what was being hidden. Ferb, Baljeet, Buford, and Candace were standing at attention, ready to listen.

Isabella, not so much.

Seeing Phineas again (and more importantly, seeing him back to his normal self) gave her butterflies in her stomach. It was making her feel whole again. As Isabella stared at Phineas, she smiled to herself. His rambling was always adorable, but this time it was even better.

"So after we deal with the invasion, there's something I need to ask of you, Isabella."

"What is it, Phineas?"

Suddenly, Phineas transformed into a centaur and offered Isabella a hand. Isabella was in awe, barely able to speak as she took his hand and went onto his back.

"Will you run off with me so we can start a new life together?"

"Of course, Phineas!"

"Great! We've got everything set for battle then."

Isabella jolted back into reality, gazing around the backyard. Phineas was looking remarkably less like a centaur, and everyone else was still here. Sighing to herself, Isabella realized that she had taken a trip to Phineasland during Phineas's explanation.

_Shoot._

"And with that, let's reveal what I've got for everyone!"

Phineas tore off the tarp, revealing five familiar mechs, in addition to a new one for Candace to use. They resembled those created for the battle against Super Super Big Doctor. As the gang admired them, Phineas cracked open a crate before tossing everyone a baseball launcher...except Isabella. She was a bit surprised, but then noticed Phineas staring directly at her.

"You mind if I talk to you real quick, Isabella?"

"Of course not!"

Phineas led Isabella to behind his own mech, where he sat down on a crate and motioned for her to sit next to him. Was… was this it? The moment she'd been waiting for? Was Phineas going to tell her how he felt?

"So, I read your letter. And as you can tell, it… affected me. I'm sorry. For everything."

"Phineas...it's okay. I should've known better than to overwhelm you with all of this. It's just that I-"

"I know. And as much as I want to talk about all of this, about us, there's a more pressing issue here. I need you to trust me."

Isabella wilted a bit, before nodding. This was a whole new side of Phineas she had never seen before. Blushing slightly, she knew it would be best to set aside what was going on in favor of dealing with the impending invasion.

"Okay crumb cake. I trust you."

Phineas smiled back at Isabella, pulling her in for a tight embrace. For a brief moment of time, it made their worries melt away. As they pulled apart, Phineas reached behind the crate to grab something.

"You may be wondering why I didn't give you a baseball launcher. That's because I was making sure yours was as high quality as possible."

Hearing those words made Isabella blush, holding her hands to her chest. Only Phineas could make something like that a romantic gesture.

"And as a bonus, I gave yours a unique feature."

Phineas handed Isabella the pink baseball launcher before pointing to a trigger on the underside.

"This trigger here will shoot a flare forward. It's good for calling for aid, as well as taking down clusters of robots, but never fire it in an enclosed space. I call it 'The Fireside Shot'."

Isabella held the baseball launcher, forming a larger smile towards Phineas. Seeing him like this was wonderful.

_It's perfect. Just like him._

"One more thing Isabella."

"Anything for you, Phineas!"

"Can you call up the Fireside Girls? We'll need all the help we can get."

* * *

Kicking down the door, Perry burst into the warehouse alongside Heinz Doofenshmirtz. Standing in a fighting stance, Perry then looked back towards an irritated Heinz.

"Perry the Platypus, remember that conversation we had about you kicking down doors about a month or two ago?"

Perry rolled his eyes as he pulled several dollar bills out of his hat, handing them over to Heinz.

"That's better. Now let's see what we've got here."

The warehouse was full of prototypes, spare parts, and assorted blueprints. Many of them were unfinished or damaged, with plenty of blast marks along the walls. Heinz's eyes were caught by four large Inators collecting dust. He strolled around them, looking intently at their designs.

"I can't remember what these Inators even did for the life of me. You know, maybe we should test them."

Perry rolled his eyes as Heinz fired up one of the Inators and stood in front of it. Blasted by a bolt of green energy, Heinz blinked several times, struggling to comprehend what just happened.

"That's a very peculiar outcome for this Inator. I don't feel any similar to how I was before I was zapped. Perhaps in my haste to test it I had a setting in an undesirable position."

Heinz proceeded to lift his left leg into the air before setting it down, allowing him to move forward. He did the same with his right leg as he made his way back to the Inator. Very slowly. Left, right. Left, right. It was almost like he was stalling for time. From a distance, Perry folded his arms and groaned to himself.

"You know, for some reason I feel like taking the slowest possible route to-WAIT A MINUTE! I REMEMBER NOW! This was the Tedious-inator! When it hits someone, it makes them perform tasks as slowly as possible! I originally designed it to..."

Heinz kept rambling on and on about the Inator as Perry slammed his face with the palm of his hand. Seeing as how the Tedious-inator was performing its intended function, he had to put a stop to it or they'd never get anything done. Perry rolled his eyes as he strolled over to the Tedious-inator, hitting the reverse switch and aiming the Inator at the slower-than-a-snail Heinz Doofenshmirtz. The laser hit Heinz, who then proceeded to rush straight into the machine and hit his head, falling onto the ground. Placing his hand over the bruise, he got up off his feet and sighed.

"Well...that's one Inator tested. Three more to go."

Heinz walked towards the next Inator, eyeing it up and down. Eventually, he raised his hand into the air as he had a realization.

"I got it! This is the Blow-itself-up-inator!"

Moments later, predictable results ensued.

* * *

While Phineas and the rest of the gang made adjustments on their equipment, Isabella leaned on a fence as she pulled out her phone. Grabbing Gretchen's contact information, she quickly placed the call.

"Hello?"

"Hey Gretchen! Can you and the troop make it to the boys' backyard? They're working on stuff to defend against the robot invasion."

Upon mentioning Gretchen's name, Isabella couldn't help but notice Ferb raising an eyebrow at her, smirking as she saw him.

_Interesting._

"Of course, chief! We'll be there right away!"

"See you then."

Isabella ended the call before walking over to assist the others. She occasionally noticed Phineas glancing up at her and blushing when she noticed him. It was cute.

_Maybe my letter did get to him._

After about half an hour of work on the machinery, the Fireside Girls arrived. Isabella ran over to them and saluted them. As she did so, she noticed Ferb glancing in Gretchen's direction before Phineas said something undecipherable at him.

"Girls! Glad you could make it."

"Any time chief."

The girls quickly pulled Isabella out of earshot of the boys, huddling around her. Immediately, gossip broke out amongst them.

"So what did Phineas say to you about the letter?"

"Did you two kiss?"

"Did he explain why he was in Candace's large intestine two months ago?"

"Did Baljeet say anything about me?"

Isabella clenched her fists as she gave the girls a glare. They backed down almost immediately to let their troop leader speak.

"All Phineas said was that he was sorry for how he treated me this summer. He did promise that we'd discuss the letter more after the invasion."

"Sounds about right. So where do you need us?"

"Just help out the guys wherever you can with their machinery! We'll need the best possible equipment if we are to defend Danville."

"Aye aye chief!"

As the Fireside Girls spread out to assist the gang, Isabella tapped Gretchen on the shoulder. She immediately turned back around and nodded at her.

"Gretchen, I do have one specific assignment I need you to assist with. It's kind of personal."

"Of course, chief! What do you have for me?"

Isabella glanced around before beginning to whisper, making sure nobody was nearby.

"I need you to keep Ferb distracted and away from Phineas."

Gretchen gave Isabella a sly smirk as she nodded.

"Can do, chief."

"Thanks Gretch. I appreciate it."

As Gretchen walked off, Isabella smirked to herself. Her plan was twofold: get Phineas and Ferb separated so she can spend more time with Phineas, and get Gretchen and Ferb closer. After all, she owed Ferb for keeping her crush on his brother a secret for so long.

* * *

"Ferb, can I ask you something?"

Phineas and Ferb were busy adjusting the wiring on Ferb's mech. Looking towards his brother, Phineas noticed that he wasn't responding to him and simply staring at gathered Fireside Girls.

"Ferb? You okay?"

Ferb jumped to attention as he got back to work on the wiring, nodding at Phineas.

"Are you mad at me for running off?"

Ferb shook his head as he continued to work.

"Well that's good. It's just that… I realized I'm in love with Isabella. Her letter said some things I never realized until last night."

Ferb smirked to himself as he kept working.

Finally. The cat's out of the bag.

"I want to tell her, but I shouldn't when all of this is happening. I just hope we can endure the invasion."

Ferb raised a finger to speak, but before he could do so, Gretchen approached the two of them. She smiled at Ferb, but he was in too much of a daze to comprehend it. His mind was like when he had the emu curse about a month ago.

"Ferb? You there? Ferb?"

Ferb jolted to attention as he looked towards Gretchen, smiling sheepishly.

"I was just asking if you could show me where you're keeping the baseball launchers."

Ferb nodded as he walked off, smiling to himself. Phineas gave him a thumbs up as he left, before glancing back at the wiring and continuing where Ferb left off.

"Need a hand?"

Phineas looked up from his work to see Isabella standing in front of him. Smiling, he gestured for her to assist him with the wiring, hoping to spend more time with her until they needed to move out. Isabella kneeled down to assist Phineas, looking towards him after about two minutes of work.

"Your brother seems happy to be with Gretchen."

Phineas glanced over to Ferb and Gretchen, who were sitting by the crate of baseball launchers.

"Yeah, he does. Maybe he has a thing for her."

"And if he did, I wonder if he'd keep it bottled up or tell it directly."

"We may never know."

Phineas and Isabella chuckled at each other while they took in the situation, working on making touch ups to the gang's equipment together. And after about another hour of work, everything was ready. Phineas jumped onto a nearby crate, attempting to get everyone's attention.

"Alright, that should be-"

_BOOM._

An explosion rocked the ground, right as Phineas was about to speak. Shielding his eyes from any oncoming dust or debris, he motioned for the gang to follow as they gazed out at Danville, or more specifically a cloud of dust rising over downtown.

What they saw… was chaos.

Buildings were destroyed. Robots were flying overhead. It was horrible. Phineas grabbed his baseball launcher as he got up off his feet and held it out towards the city.

"I know what we're going to do today."

**Notes for the Chapter:**

> And that's our chapter! I should note that next chapter will primarily revolve around Perry and Heinz since the kids would be fighting off the invasion in the streets. Make sure to leave a review and a follow if you enjoyed!


	6. Conflict

**Summary for the Chapter:**

> Battle rages on the streets of Danville. While Phineas makes a discovery regarding a past invention of his, Perry chooses to disobey his superiors in favor of aiding Heinz Doofenshmirtz.

**Notes for the Chapter:**

> I am SO sorry for the delay on this one! I was going through multiple ideas for it, some irl stuff happened, and I had a bit of delay with beta reading, both for my fic and a friend's. Not to worry though, because Cake's Crumb is back!

Several arduous, painful, and memorable minutes of testing had resulted in Perry and Heinz figuring out which Inator in his warehouse was which. Leaning on the Tedious-inator, Heinz slouched onto the floor next to Perry as he sighed.

“So this is the Tedious-inator, that over there is the Peel-inator, which I’m glad I added a reverse switch to, that’s the Depower-inator, and that over there is the remains of the Blow-itself-up-inator. I should really start labeling these things, shouldn’t I?”

Perry gave Heinz a look of annoyance, sighing to himself. The two of them had blown themselves up, lost electricity in the warehouse, and had to see a skinless Heinz Doofenshmirtz. Just as Perry was finishing flashing back however, he heard his watch beeping, accompanied by a familiar voice.

“Agent P? Come in Agent P!”

Perry quickly activated the watch’s video function, coming face to face with one Major Monogram.

“Agent P, we need you to return to O.W.C.A. headquarters immediately! Danville is overrun, and-”

“Oh hi Francis! How’s the wife?”

“Is that Dr. Doofenshmirtz I’m hearing, Agent P?”

Perry gave Monogram a sheepish grin as he shrugged.

“Unfortunately, due to budget cuts and security concerns, we cannot allow the two of you to work together this time.”

Perry chittered angrily.

“Agent P, you MUST return at once!”

Perry chittered back.

“Do not sass me Agent P! You must-”

Tired of the conversation, Perry chittered in chunks to imitate the effect of him cutting out, right as he turned off his watch and groaned. He was definitely going to be on latrine duty next week.

“Perry the Platypus! You’d defy Francis to work with me?”

Perry nodded as he smiled. His choice to work with Doofenshmirtz was twofold: he knew Norm better than anyone, and he was also extremely dangerous and needed to be watched.

Perry also had a third, more secretive reason. That was his friendship with Heinz.

* * *

Downtown Danville was in chaos.

As robots flooded the streets, a battle raged. At the forefront of the defense were Phineas, Ferb, Isabella, and their friends, baseball launchers and impromptu inventions in hand. Phineas’s mech was struck by a stray laser beam. Escaping the wreck, he leapt out with his baseball launcher, firing a baseball at the robot responsible. Wiping sweat off of his brow, Phineas took a look at the robot’s remains. Its beaked head was familiar. Almost too familiar.

“Hey Ferb, is it just me or does this robot look like our Beak suit?”

Ferb poked his head out of his mech as he eyed the robot. After a few seconds, he gave Phineas a thumbs-up.

“Huh. I guess our blueprints must’ve leaked somehow.”

Phineas, clenching his baseball launcher, looked up from the robot’s remains to see Isabella standing on top of a destroyed robot. Glaring out at the battlefield, she got into a defensive position.

“Alright, who wants some?”

Isabella’s yell caught the attention of several robots. They gathered and charged for her along the street. Grinning, Isabella fired off a baseball, maneuvering it through multiple robots. The impact would daze them and leave them vulnerable. Isabella then performed a quick somersault forward before firing off her launcher’s Fireside Shot. The results were nothing but countless piles of scrap. Blowing smoke off of her launcher, Isabella looked behind herself to see Phineas looking on in awe, speechless.

“How did I do, Phineas?”

“I am so in love with you right now.”

“What?”

“What?”

Phineas shook his head as he blushed to himself. Isabella smirked in response while the group surveyed the damage caused by the skirmish. So far, Phineas and Isabella had lost their mechs entirely, Buford’s had sustained heavy damage, but the robot swarm was mostly contained. Phineas stood on top of the remains of his mech to address the group.

“Alright everyone, we have a brief moment to rest up before we figure out our next move.”

As everyone took a moment to relax, Phineas sat down on top of one of the robots, Isabella next to him.

“You know, these robots resemble-”

“Yeah. Our Beak suit. I thought we made sure this project wasn’t put on our website, but I guess not.”

Phineas sighed to himself as Isabella put her hand on his shoulder reassuringly.

“If they’re using robots based on your Beak suit, wouldn’t that make things easier for us? You know the suit after all.”

“I guess. It just makes me wonder what kind of effect we’ve had during the summer. I didn’t want our ideas to be used for this.”

Isabella smiled at Phineas in response, getting up on her feet.

“You built a massive rollercoaster! You saved summer itself! You even stopped a pharmacist apocalypse for crying out loud! I know I’ve gone on a rant like this before, but you need to see that the positives outweigh the negatives here! If we can do all those things, surely we can stop a robot invasion!”

Phineas smiled back at Isabella, getting up off of the scrap. He then looked further out at the city, noticing the source of the robots.

“Seems like the robots are coming from that building shaped vaguely like Ferb’s head.”

“Isn’t that where Vanessa’s dad lives?”

“I think so. Either way, we’d be easily noticed if we went in a group.”

“Perhaps the smart thing to do would be for us two to head in there together.”

Phineas looked towards Isabella, who was blushing slightly. Smirking in response, he looked to the rest of the group, trying to get their attention.

“Guys, Isabella and I are going to be heading for the source of the invasion. Ferb, keep an eye on everyone’s machines.”

“Gretchen, make sure the troop is in order.”

Ferb and Gretchen nodded in response as Phineas and Isabella snuck through a nearby alley. Taking position on top of the remains of Phineas’s mech, Gretchen addressed the remainder of the group.

“While Phinabel-er, Phineas and Isabella are conducting their stealth operation, let’s move further into the city. With them going ahead to that building shaped vaguely like Ferb’s head, we’ll have an easier time once we reach it.”

* * *

Heinz and Perry barrelled through the streets of Danville, riding on top of a tank-like Inator. Rather than wheel around three vulnerable inators, Heinz had chosen to combine them into one large device to make combat easier. As a robot neared the duo, Perry leapt on top of the barrel of the Inator, unleashing a tail swipe that cut off the robot’s head and left it to be crushed underneath the tank’s-

“It’s an Inator! Not a tank for crying out loud!”

Right.

The Inator wheeled through Danville, firing off blasts of energy at nearby robots. They’d lose their armor and become extremely vulnerable to Perry’s attacks, lose power and crash to the ground, or attack extremely slowly and open themselves up to being hit.

“Nice work Perry the Platypus! We make a great team, don’t we?”

Perry smirked as he heard Heinz’s words, continuing to dash and leap along the roof of the Inator as he hit nearby robots. When the duo rounded another corner, they saw a horde of robots surrounding someone.

“You know what to do.”

Perry nodded at Heinz as he leapt off of the tank, grabbing one of the robots by the head. As the others sought to attack the platypus, Heinz began to activate the Inator’s weapons, cackling to himself. Stray blasts went firing all over the street. The robots, left vulnerable, were easy pickings for Perry.

“Phew! Well that was-”

“Dad?”

Immediately, Heinz looked to see who the robots had surrounded: his own daughter. Vanessa Doofenshmirtz.

“Vanessa! Thank goodness you’re okay!”

Heinz clambered out of the Inator, hugging his daughter tightly. Perry stood by, smiling fondly. As Heinz broke off the hug, Vanessa looked to him with concern.

“You did this, didn’t you Dad?”

Heinz nervously laughed as he scratched his neck. Vanessa rolled her eyes as she gave him a deadpan look.

“Maybe. Maybe.”

“Norm literally gave a broadcast about what’s going on. Dad, how could you mess up this badly?”

“I try my best sweetie.”

Heinz glanced back to see Perry facepalming.

“Aaaaanyways, we should probably get going to stop Norm.”

“Yes, yes we should.”

* * *

Isabella and Phineas darted through the streets of Danville, being sure to avoid patrols of robots. Along the way, Isabella couldn’t help but ponder to herself. Phineas seemed focused as usual, much to her dismay. Yet, she knew that what they were braving was but a stepping stone to the moment she had desired since the two of them first met. Standing behind a dumpster as a robot scanned an alley, Phineas looked to Isabella as she looked up at the building the robots were coming from, giving her some hand signals to move out. Isabella nodded as they rushed into another nearby street, darting behind a tree. The situation the two of them were in reminded her of the Pharmacist apocalypse a few weeks back, when she had been attempting to gain her Emotional Bravery Patch by telling Phineas how she felt. Isabella sighed to herself as she remembered that day.

“Isabella, you seem out of focus. Everything okay?”

“Peachy.”

Phineas gave Isabella a look of concern as he motioned to keep moving through the streets. Hiding behind a statue, they barely avoided a patrol of Beakbots passing through.

Save for one that just happened to be glancing back at them.

Brandishing a palm-mounted laser cannon, it began to fire at the kids as they darted away, using their baseball launchers to rack up damage in response. After a few seconds of back-and-forth shooting, the robot neared Isabella. Unleashing a ferocious punch, her baseball launcher was knocked out of her hands. Isabella dived behind a nearby mailbox in an attempt to take cover. Phineas, watching this, clenched his fist as he dived for Isabella’s stray baseball launcher. Clenching it, he rushed on top of a garbage can, brought out his own launcher, and fired off both launchers at once. Two baseballs struck the robot in the back at lightning speed, sending it to the ground. Isabella poked her head out towards Phineas, who was offering her a hand to get up. Blushing, Isabella took the hand as the two of them looked to their surroundings.

“We made it.”

“And now, it’s time for the hard part. Everyone’s counting on us, crumb cake.”

Phineas blushed slightly upon hearing that nickname, something Isabella caught onto. Something told her that she would be getting something to remember after all of this was over.

**Notes for the Chapter:**

> And that's our chapter! I should note that there are going to be at least four more chapters, possibly more depending on how I want to write to the ending. Make sure to like, follow, and review! Also, a special thanks to ThiaQuiche and Thecactus1 for beta reading!


	7. Choices

**Summary for the Chapter:**

> Phineas and Isabella have reached the top of Doofenshmirtz Evil Incorporated, with the final battle for the fate of Danville about to begin.

**Notes for the Chapter:**

> Hey guys! Another chapter is finally here, and I can confirm that the next chapter will be the last one. However, this won't be the end for my fanfiction! I'm planning to do a series of oneshots designed akin to episodes that take place in the summer following the main series and this fic as my own "Season 5" of Phineas and Ferb more or less! Keep an eye out for those.

Ferb, Gretchen, and their allies moved through the streets of Danville, surrounding the purple building Phineas and Isabella were inside. By now, everyone's mech had been destroyed, and there was nothing but fallen robots and rubble on the streets. Gretchen took a seat on a nearby bench, accompanied by Ferb. She sighed to herself.

"I hope Phineas and Isabella are okay up there. We're all counting on them. I just hope we can support them for long enough."

Gretchen's worries were largely due to her being abruptly left in charge of the team alongside Ferb. Despite being Isabella's second-in-command, she wasn't exactly ready for this opportunity. They had made it to the building, but not without a cost. Ferb had begun to realize this, putting his hand on her shoulder and smiling. Gretchen looked back at him, smiling in response.

"Thanks Ferb. Let's get everyone mov-"

Gretchen's sentence was interrupted by the ground below the duo rumbling. Nearby, the rest of the gang was panicking, with Buford pulling Baljeet onto his shoulder.

"Buford, why did you-"

"Gotta keep my nerd safe!"

Suddenly, the rumbling stopped. Everyone looked to each other, confused as to what happened. Then, Adyson looked up near the building as she screamed.

"Look!"

The group gazed out at the skyline to see a massive, hulking robot leaning on the side of the purple building. Smashing its fist into a nearby skyscraper, it let out a defiant roar.

One hell of a battle was about to begin.

* * *

Phineas, clenching Isabella's hand, rushed through a hallway as a pair of Beakbots chased them down. Firing off a baseball at one of them, he dived around a corner into a nearby stairwell, slamming the door and pushing on it to keep their adversaries away. Letting go of Phineas's hand, Isabella secured her baseball launcher, aiming it at the door. When Phineas eventually gave way for the door to crack open, the two robots rushed right into Isabella's shot, slamming into each other and collapsing to the ground. Phineas kicked the rubble before looking up at the stairwell.

"Shame the elevator wasn't working. I really don't like stairs."

"You and me both."

Phineas and Isabella began to ascend the stairwell, holding their weapons tightly and looking around. As they did so, Phineas realized how many stairs there were, as well as how he'd have to figure out a way to kill time as they walked. Then, it dawned on him: he could confess to Isabella now! He could give the two of them the boost they needed to stop whatever was at the top! At the same time though, Phineas knew that he had to focus. If he slipped up, he could get himself and Isabella in trouble. His mind raced back and forth for several minutes until he made a decision.

"Isabella, I-"

"-think we're here?"

Phineas realized that they had reached the top of the stairwell. Mentally cursing himself, he looked towards Isabella.

"...yeah. We're at the top."

Phineas creaked open the door carefully, seeing an empty hallway. Motioning for Isabella to follow, the two of them snuck through carefully, hearing noise from one specific apartment. Phineas attempted to open the door, but it was shut. That is, until Isabella kneeled down by the doorknob and pulled a small file out of her pocket.

"Lockpicking Patch."

"You're prepared for everything, aren't you?"

"A Fireside Girl is always prepared."

Isabella finished up her lockpicking as the door creaked open. Carefully stepping inside, the two of them had their backs to each other, surveying the dark room. Nothing but small lights and a few monitors could be seen.

"Something feels wrong Isabella."

"You're right. Something does-"

At that moment, a massive monitor turned on, bearing the face of the robot from the broadcasts.

Norm.

"Hello children! I'm very disappointed that you decided not to surrender."

Two massive robotic arms extended from the monitor towards the duo. Phineas and Isabella dove out of the way before firing off their baseball launchers at the arms, knocking them away. When they came back around for round two, Phineas and Isabella leapt away again, continuing to batter the arms with baseballs. The fight went back and forth for some time, up until Phineas had kicked down one of the arms, pinned it down, and was proceeding to shoot at the eye in the center.

Without paying attention to what was behind him.

"PHINEAS!"

Phineas had failed to notice the other arm extending towards him until he was actually clenched by it. It pulled him upwards towards Norm's monitor as he struggled to break free. Isabella, standing before Norm, shed a tear as she clenched her weapon.

* * *

Doofenshmirtz, Perry, and Vanessa were tearing through robots on their way to Heinz's building. The "Three-In-One Inator", as Heinz had dubbed it, was making quick work of the trio's opposition as they moved through the streets. Eventually, they had arrived at the plaza near Doofenshmirtz Evil Incorporated, where a giant robot was fighting off multiple children. For some unknown reason, Perry had darted inside the Inator right as they arrived.

"What is Perry the Platypus doing?"

"I have no clue Dad."

Heinz and Vanessa gazed out at the battlefield, noticing the giant robot being slammed against his building.

"Sadly we'll need to get closer if we're able to land a shot."

* * *

Perry was nestled inside the cockpit of the Inator, manipulating several dials and switches as he aimed at the giant robot. Wiping sweat off of his brow, he pulled the trigger to fire as he set the dial to "Peel".

* * *

A beam of energy fired from the Inator at the robot as Doofenshmirtz and Vanessa look on in astonishment.

"I stand corrected."

* * *

The battle against the giant robot was in full swing as the Fireside Girls, Ferb, Buford, and Baljeet held their ground. The air was full of baseballs and other weapons being shot at the robot, but it was protected from it by a dense layer of metal armor. Gretchen, diving away from a fist hammering down on the street, looked to Ferb, who was firing off another baseball into the air.

"Ferb, we can't make a dent in that thing! We'll need some serious firepower to take it out!"

At that moment, a massive green beam struck the robot from out of nowhere. Immediately, the metal shell protecting it fell to the ground with a resounding thud, revealing its skeleton to be made of wood. Ferb gazed at it for a few seconds, immediately recognizing it.

It was their treehouse robot.

Ferb grabbed Gretchen's hand right as the robot slammed down another fist, climbing onto it with her. As the robot raised its fist again, the two of them began to climb the arm, towards the cockpit. Gretchen had a nervous expression on her face.

"Ferb, are you sure this is safe?"

Ferb glanced back at her, giving a thumbs-up. After some more climbing, the duo reached the cockpit, which was surprisingly empty. Ferb immediately kneeled down to the control panel, opening it up and beginning to fiddle with the wires.

"I really wish I got my Hotwiring Patch…"

* * *

"Miss Garcia-Shapiro, you're quite the stubborn little girl."

Norm's monitor loomed over Isabella as she stood next to the broken metal arm. In his other arm was Phineas, gasping for air as the metal grip on him tightened. The two of them looked to each other with expressions of worry, as if their fates were intertwined.

"I-Isabella!"

"Lucky for you, I'm a robot who's willing to negotiate!"

The arm holding Phineas extended outwards, towards the balcony of the building. Isabella, clenching her baseball launcher, looked to him.

"Save Danville, or save the one you love. Unless the situation has changed in the last 24 hours, I have accounted for every possible scenario. You cannot win Miss Garcia-Shapiro."

Norm's steely glare gazed down at the young Fireside Girl, who was now glancing at Phineas, then turned to Norm. Then to Phineas. Then to Norm. As she did so, her mind was racing. Voices entered her head.

"Isabella, you can't let Phineas die here!"

"Isabella, you need to save Danville! Set your crush aside!"

"This trigger here will shoot a flare forward. It's good for calling for aid, as well as taking down clusters of robots, but never fire it in an enclosed space."

Hearing Phineas's words in her head, Isabella gazed at Norm as her finger neared the orange trigger on her baseball launcher. Aiming it at him, she grinned to herself.

"I've decided what I'm doin'."

"Great! What is your decision?"

"Turning you to ash."

Isabella pulled the trigger as a flare rocketed out of her baseball launcher, heading straight for Norm. Phineas, gazing at it, gave Isabella a look of worry. And as for Norm, his eyes widened as he uttered his last words.

"He...he knows you love him…"

The flare hit Norm, unleashing a ferocious explosion throughout the laboratory. The impact caused Phineas to be released from the robot arm, but he ended up sliding along the floor, right to the edge. As Isabella pushed away the fog, she gazed towards Phineas, screaming in response as she saw him clinging to the edge.

"PHINEAS!"

Isabella dashed to Phineas, attempting to pull him up. As she did so however, a nearby Beakbot ended up crashing into the building and exploding, shaking the ground and causing her to lose her grip. Phineas was now plummeting to the ground, staring into Isabella's eyes. For a few seconds, time seemed to stand still as the two lovers looked to each other. Isabella even swore she saw Phineas mouthing the words "I love you".

"Gotcha!"

Out of nowhere, a giant wooden robot rose above the building, Phineas in its hand. Ferb and Gretchen sat in the cockpit, high-fiving each other.

"Whoa, you rebuilt the treehouse robot Ferb?"

"More like hotwired one Norm was using."

Isabella clambered onto the arm as she entered the cockpit, alongside Phineas. Both of them had a few bruises, as well as soot covering their bodies, but they grinned sheepishly at each other.

It was finally over.

* * *

The treehouse robot, alongside the Fireside Girls, Buford, and Baljeet, now stood outside Doofenshmirtz Evil Incorporated, where the wreckage of countless robots dotted the ground. Phineas, Ferb, Isabella, and Gretchen jumped out of the robot as they looked to their friends.

"Whatever you two did up there, it caused all those robots to explode."

"I guess we can consider today seized, right Ferb?"

Ferb gave Phineas a thumbs-up as the group looked to each other curiously as if to say "What now?". Eventually, Baljeet formed a smile.

"Oh! Why don't we go watch the new Doctor Zone episode? It's due to premiere in half an hour!"

"Good idea Jeet! I was gonna play baseball with the complimentary launcher but it was taken by a raccoon after all the robots went kablooey."

Baljeet snickered at Buford, muttering the word "karma".

"What?"

"N-nothing."

As the gang walked out of the plaza, Phineas grasped Isabella's arm as if to stop her. She looked back at him, blushing and smiling madly.

"Hey guys! Isabella and I might be a bit late. We have some unfinished business to discuss back at my place."

The duo walked towards Phineas's house, both of them feeling nervous.

This was it.

**Notes for the Chapter:**

> Finally, our climax has come and gone! Hopefully you guys enjoy! Next chapter is not only the finale, but also the chapter you've been waiting for!


	8. Lovers

**Summary for the Chapter:**

> Phineas tells Isabella how he truly feels about her.

**Notes for the Chapter:**

> Here it is. The final chapter. I've been waiting to do this one for a while, and we'll be cutting right to the chase for the confession. Stay tuned after the fic however for a message from me!

The sun was beginning to set as Phineas and Isabella walked down the street, towards the Flynn-Fletcher residence. Holding hands, Isabella glanced towards Phineas, who smiled back and blushed slightly. Isabella smiled back as she blushed to herself, the two of them walking in silence for some time. When they did arrive at the Flynn-Fletcher household, Phineas opened the gate to the backyard, walking over to the tree. It was this tree that held many, many memories for the two of them.

“Every time I come out here in the morning, I end up reminiscing about everything that has happened near this tree. Everything I...no, we, have done this summer.”

Isabella blushed as she heard Phineas emphasize the word “we”. He seemed different to her, not that she minded. Phineas walked over to the trunk of the tree, tapping it twice as a large egg emerged from it, opening up.

“Remember when Ferb and I were the Beak? We ended up making a little nest up in the tree for that day, and I sort of keep it as a personal spot of mine.”

Phineas sat inside the egg, offering his hand to Isabella as she sat next to him, smiling. The egg closed as it ascended into the tree, popping up onto the floor and cracking as Phineas and Isabella exited it.

“Welcome to the Nest Isabella.”

Isabella gazed around at the Nest, noticing a large computer and a Beak suit in a cage. Of particular note to her was a balcony however, concealed by several leaves. Phineas walked over to the balcony as he pressed a button, parting the leaves to reveal a view of the sunset. He sat down on the bench, offering Isabella a seat next to him. She sat down, looking towards Phineas in curiosity. He sighed as he twiddled his hands.

“So...the letter.”

“Yeah.”

“Looking back, I...I was a huge jerk to you Isabella. How could I have missed all of this? Every subtle advance, every offer for me to spend time with you, every flirtatious comment...I’m an idiot for not noticing!”

“No you’re not Phineas! You’re brilliant in every way. If anything, it was my fault for not being obvious enough.”

“Yet you kept going.”

Isabella glanced over to Phineas curiously, shedding a tear as she did so.

“Wh...what?”

“Even when I seemed dense or oblivious, you kept on trying. You never gave up on me even when you had a good reason to. I never realized how lucky I was to have someone like you!”

By now, Phineas seemed to be angry as Isabella put a hand on his shoulder reassuringly.

“I want to ensure that I can be there for you Isabella. That I won’t mess up again! Romance has never been my strong suit.”

“But there was the ship with Baljeet and Mishti! And all that stuff you did for Candace and Jeremy! And-”

“I know. But with you, I’m more worried. I want it to be perfect. I want no mistakes. I…”

Isabella held Phineas in a tight hug in an attempt to calm him down, patting his back. She couldn’t help but cry, grasping him tight.

“Phineas, I love you for who you are, not what you can do for me.”

Phineas looked up at Isabella, eyes tearing up, as he continued to hug her. The two of them remained in each others’ arms, enjoying the moment, until Phineas broke the hug and looked into Isabella’s eyes.

“I-Isabella?”

“Yes Phineas?”

“Can...can I do something for you?”

“Of course! Wh...what is it?”

“This.”

Phineas leaned in to give Isabella a kiss on the lips, quickly pulling back right after. He was blushing to himself, smiling nervously.

“I...I love you Isabella Garcia-Shapiro. You’re amazing.”

Isabella, looking back at him, was struggling to find the right expression to express her happiness. He kissed her! He finally told her he loved her! She shed a tear as she stared at her red-haired crush.

“Isabella, you okay?”

“I’m more than okay.”

“Wh...what?”

Isabella pulled Phineas towards her, engaging in a kiss back. Unlike Phineas’s kiss, Isabella thought the two of them deserved more. Electricity sparked between them, almost as if fireworks were going off inside the two of them, as they basked in their moment together. Eventually, as Isabella broke off the kiss, she smiled at Phineas, blushing to herself.

“I gitchee gitchee goo you too, my little crumb cake.”

Phineas’s eyes were wide open as he gazed at Isabella fondly, a blush forming on his face.

“Wow.”

Isabella leaned on Phineas’s shoulder as he wrapped an arm around her, the two of them blissfully enjoying each others’ presence in silence.

* * *

Perry, Heinz, and Vanessa made their way into Heinz’s building, finding nothing but scrap and wreckage inside. Multiple destroyed Beakbots, the remnants of Norm’s traps, and two massive metal arms dotted the ground. Heinz sheepishly rubbed the back of his neck as he looked around.

“At least I can salvage Norm’s equipment for my own purposes! Right Vanessa?”

“Dad, why does it matter? Perry is gonna bust it up anyways.”   
“Well...erm…”

Heinz glanced over at Perry, who was smirking at him. As he did so however, his watch began beeping as he took the call. It was Major Monogram.

“Agent P, you’ve done the Tri-State Area a great service. And disservice.”

Perry blinked a few times as he attempted to process Monogram’s words.

“You defied my orders, but you also allowed those kids to defeat Norm. For that, I’m only putting you on litterbox duty for the next two days.”

Heinz began to cackle upon hearing Francis’s words as Vanessa stood by, facepalming.

“Don’t worry Perry the Platypus. I’ll be sure to take a break from evil once you’re done your DUTY!”

Heinz began to cackle again, before being slapped by Vanessa. He put his hand over the bruise as he sighed.

“Alright, it wasn’t as funny the second time.”

Perry stifled a laugh as he looked back to his watch.

“See you tomorrow at headquarters Agent P. And bring at least ten bags. Monogram out.”

Monogram’s visage faded out as Perry glanced up at Heinz, offering a handshake. Heinz took it as he smiled at his platypus friend.

“I have to sort out insurance with the blown-up apartment anyways. Oh, and make a new Norm! Good thing I always back up his hard drive!”

Perry gave Heinz a thumbs-up as he walked to the edge of the building, got out his glider, and flew off into the night.

* * *

Phineas and Isabella strolled towards Baljeet’s house, failing to notice the platypus hang gliding above them. They were preoccupied with a conversation as they held hands along the street.

“You know, that kiss felt familiar to me. I don’t know why.”

“Hey, at least we did it now instead of waiting ten years for us to get together. I can’t imagine how disappointing that would be.”

Hearing those words, Perry dived to his right as he glided, right into a bush. Shedding his hat, he emerged from the bushes right in front of Phineas and Isabella, chittering to them.

“Oh there you are Perry! Just in time for Doctor Zone! And plus, something amazing happened while you were gone.”

Isabella petted Perry on the head a few times as Phineas lifted him into his arms, smiling at Isabella. Perry was quick to notice the way the two of them were staring at each other, smiling to himself.

“Now then boy, let’s meet with the others.”

Phineas and Isabella strolled through Baljeet’s backyard, towards the open patio door. There, the whole gang was huddled around the couch watching the episode. Phineas and Isabella’s arrival caused Baljeet to pause it however.

“Hey guys! Sorry we’re late. We had to, erm…”

Phineas clenched Isabella’s hand as he smiled at her fondly. She returned the smile, with an added blush. The rest of the group was in shock, save for Candace. She was simply smirking.

“Looks like I win the betting pool.”

Everyone grumbled as they handed Candace dollar bills, with the occasional phrase being discernable.

“Why did I bet on it happening ten years from now?”

“Can we do a bet with me and Baljeet?”

“What?”

“Nothing.”

Phineas and Isabella stared down Candace as she took the last dollar bill, shrugging right after.

“What? We set up a betting pool for when you two would get together, and I won.”

“How long did said betting pool exist?”

“Three years.”

“I must have missed a lot of hints.”

“Yes, yes you did.”

Isabella clenched Phineas’s hand tighter as the two of them sat down on the couch, Isabella resting her head on Phineas’s shoulder. Baljeet pressed the play button, and the gang got to watching the Doctor Zone episode.

For Phineas and Isabella, this would be a day to remember.

**Notes for the Chapter:**

> There it is. Cake's Crumb is now finished! Thank you everyone for reading, and keep an eye out for my next fic, taking place at the start of the gang's next summer! Should you wish to talk to me, my Discord is Krex#0843!


End file.
